you're fine
most of the time the Mac will send the "raw" file to the aTV and it will be played there.
there is this, but it can run into compatibility problems if you're not playing media from apple.
you must use specific file formats. I don't use this, and don't know where you got your files, so not sure how offten you may run into issues.
Stream content from your computer's iTunes library to other computers, iOS devices, and Apple TVs.
support.apple.com
If the file format isn't comatible with the aTV, you have a couple options,
Re-convert it with handbrake or similar to make it work. This might be problematic with HDR videos
or look at a program like plex. (this is what I do)
it categorizes all your media for you, the Mac will run a server program, that tags all of your media, and gives you a "Netflix like" experience on the aTV.
there are some basic ways you need to organize your files, but it's simple and broken down on their website.
then you just point plex to that folder, and it handles the rest.
it also keeps track of what you've watched, helpful when working through TV shows.
There are plex client apps for pretty much everything, iOS, android, Mac, windows, linux, most streaming boxes (appleTV, roku... etc) as well as most smart TVs.
if the file isn't compatible with the player, the server will convert it
plus since it's server based, you can stop something on the aTV and pick it up on your phone.
it will work for free, but with a paid subscription, you add features like being able to sync media to your phone, so you can watch offline
it also allows you to connect remotely as long as your internet connection speed can support it.
you can also invite friends to share your server, and they also can watch your library wherever they are.
and obviously, no matter which way you go, your Mac must be awake, the screen can be off, but it must be powered on, and not sleeping.